The overall objectives of the research project are the following: 1. Screening of individuals with acquired or inherited abnormalities in host defenses for defects in phagocytic cell function in order to better understand the mechanisms by which normal leukocytes operate. 2. Definition of the mechanisms involved in oxidative metabolism of phagocytes and their relationship to other non-oxidative mechanisms which mediate intracellular antimicrobial activity. 3. Investigation of the opsonic requirements and cellular receptors for phagocytosis by macrophages from several different sites. Studies of the mechanisms utilized by these cells for intracellular killing and their relationship to enhanced cellular immunity or "activation."